1. Field of the Disclosure
The present disclosure relates to a diagnostic system and calibration system for analyzer devices, and in particular, to a system for the diagnosis and correction of device properties of an inductively coupled plasma mass spectrometer (ICP-MS).
2. Discussion of the Background Art
The ICP-MS is known as a high-sensitivity analyzer for detecting traces of metal ions. By means of this analyzer, a sample to be measured is introduced inside the plasma and the sample to be measured becomes ions, these ions are extracted, and mass analysis is performed, and the basic structure of this spectrometer comprises a plasma-generating part for generating plasma from a sample such as a liquid, and a mass-analyzing part for extracting ions from the generated plasma and analyzing these ions.
The plasma-generating part, particularly in the case of a liquid sample, comprises a nebulizer for nebulizing a liquid sample using a gas having a specific flow rate; a spray chamber for isolating some of the nebulized liquid drops in the form of an aerosol together with an appropriate gas; and a plasma torch such that plasma is generated from the plasma gas and the aerosol is introduced into this plasma.
In further detail, the aerosol is generated by at least some carrier gas being introduced into the nebulizer together with the liquid sample. When this portion of carrier gas blows the liquid sample, the liquid sample is nebulized. The nebulized liquid drops circulate inside the spray chamber, and only the liquid drops that are relatively small in diameter are transferred toward the plasma torch. These liquid drops of a small diameter, together with the carrier gas for nebulization, form the aerosol and are introduced to the plasma torch. The carrier gas is usually an inert gas, typically argon gas.
The plasma torch comprises an inside pipe into which aerosol containing sample is introduced and one or a plurality of outside pipes disposed such that they surround the inside pipe. Auxiliary gas and plasma gas for generating the plasma can be introduced into the outside pipe. Once the plasma has been generated by the plasma gas through the operation of a work coil, the aerosol containing the sample is introduced and as a result, the metal in the sample is ionized and dispersed in the plasma.
An interface that faces the generated plasma is disposed at the front end of the mass-analyzing part, which is located posterior to the plasma generating part. The interface has a two-step structure of a sampling cone and a skimmer cone, and each of these has an orifice for extracting the ions from the generated plasma. Extractor electrodes for extracting the ions in the form of an ion beam is disposed posterior to the interface. The extracted ion beam is guided to the mass analyzer disposed at the subsequent part and the measurement process of mass analysis is performed. The analysis results can thereby be obtained in the form of a mass spectrum.
The analyzer may have a computer. The computer is used in order to provide control signals such that the flow rate of the gas used is controlled, or to break down the analysis results and perform various other processing tasks. The computer can be used in combination with a user interface comprising an input device and a display device in order to provide the desired effect.
A high-matrix sample is an example of a potential sample to be analyzed by such a device. A “high-matrix sample” is a sample that contains the elements to be measured as well as water-soluble substances, such as metal salts in high concentration samples. Seawater is an example of a high-matrix sample. When a high-matrix sample is analyzed by conventional methods using conventional devices, there are problems in that, as a result of large numbers of ions being guided to the tail of the device, oxides and the like are deposited and pollute the surfaces of the sampling cone, skimmer cone, etc., and the orifices become clogged, making analysis impossible. Consequently, in the case of analysis of such samples, it is necessary to reduce the amount of matrix material entering the mass analysis part via the interface.
A single mass spectrometer capable of high-sensitivity analysis of liquid samples and having a wide range of matrix concentrations would be very effective for practical use. The method whereby a highly concentrated sample that cannot be analyzed directly is diluted to an acceptable extent before aerosol generation is one example. Dilution can be conducted manually or automatically using an autodiluter. For instance, Patent JP Unexamined Patent Publication (Kokai) 11-6788 and JP Unexamined Patent Publication (Kokai) 1-124,951 describe methods for diluting a liquid sample using an autodiluter.
Performing dilution by hand takes time. Diluting many samples is particularly an inconvenience in terms of time, and there is also the chance that there will be errors in dilution. Therefore, there is a need for an automated system for the diluting procedure, as described in Patent References 1 and 2. Nevertheless, there is the chance that the sample will be contaminated by the outside environment or the tools that are used during dilution of the liquid sample.
From this viewpoint, there is a need for novel means for dilution with which it is possible to realize excellent reproducibility and to guarantee a sufficiently wide dilution range by means different from means for diluting a liquid sample in a liquid state. In this case, it is necessary to minimize the operating time by the user. It is particularly necessary to guarantee convenient user operation when there are any parameters that determine the operating status of a device, such as the above-mentioned device. This operating convenience is also effective in preventing errors in measurement data that are generated by misuse of the method.
The applicant previously proposed control means such that the status of the plasma facing the interface changes in JP Application (Tokugan) 2006-219,520 filed prior to the present application as one means for analyzing a sample comprising matrices of various concentrations with good reproducibility using the above-mentioned inductively coupled plasma mass spectrometer. By means of this method, it is possible to reduce the number of ions that pass through the orifice of the interface and analyze with good reproducibility by changing three primary parameters under specific conditions. These three primary parameters are the output of the high-frequency power source, which determines the status of the plasma itself; the flow rate of the carrier gas that transports the liquid drops in the aerosol that is fed to the plasma torch; and the distance between the plasma torch and the interface (sampling depth hereafter). It should be noted with regard to the third parameter that this parameter is more precisely one that indicates the distance between the end of the work coil and the interface. Usually the work coil and plasma torch are anchored at specific positions correlated with one another; therefore, in the Prior Art and Description of the Disclosure, the two versions of the third parameter are regarded as the same, and are described as the distance between the plasma torch and the interface.
By means of this method, when a high-matrix sample is analyzed, the various parameters are set such that the number of ions passing through the interface is minimized and sensitivity is reduced, while when a low-matrix sample is analyzed, the various parameters are set such that the number of ions passing through the interface is increased and sensitivity is increased. It is possible to interchangeably or continuously analyze high-matrix and low-matrix samples by controlling the parameters in this way.
The first problem with this method is that the measurement results tend to fluctuate because, in addition to drift, and similar problems in the three primary parameters, there are many parameters that affect the number of ions that pass through the interface, specifically, that affect the measurement sensitivity, including those that are difficult to control. Specific examples of other parameters are sample liquid transport conditions and the fine-tuned status of the equipment. In essence, there is a problem in that even if analysis is conducted by one device, there is a problem in that measurement sensitivity will change and the measurement data will fluctuate as a result of slight deviations in any of these many parameters.
The second problem with this method is that there are many control parameters, as mentioned above, and there tend to be differences in properties between devices. In essence, even if the device structure is the same, differences in properties are produced with slight deviation between devices in terms of any of the above-mentioned parameters. This is problematic in that, for instance, it complicates the tuning procedure performed by maintenance personnel.
Therefore, the present disclosure provides a diagnosis and calibration system with which it is possible to diagnose the properties attributed to plasma of an inductively coupled plasma mass spectrometer in a short amount of time, and it is possible to automatically change the settings of the device such that they are optimized as necessary with the intention of alleviating the problems associated with the existence of many parameters.